具有可变增益恒压特性的双线圈无线电能传输系统补偿网络设计与分析

Analysis and Design of Compensation Network for Two-Coil Wireless Power Transfer System with Variable Constant Voltage Gain Characteristics

为了实现具有恒压特性的双线圈无线电能传输(WPT)系统中补偿网络的优化设计,该文在变压器T网络模型基础上定义等效耦合系数kr与等效变比n1,为双线圈WPT系统的高阶补偿网络设计与分析提供一种新方法。首先建立变压器T网络等效模型,给出具有恒压特性的串联-串联(S-S)型双线圈WPT系统元件参数表达式。其次结合等效耦合系数与等效变比,提出具有可变增益恒压特性的串联/并联-串联(SP-S)型与串联/并联-串联/并联(SP-PS)型双线圈WPT系统的补偿网络参数确定的新方法。在此基础上,考虑寄生电阻对系统传输特性的直接影响,以WPT系统的电压增益稳定性与传输效率为指标,得出不同等效参数下传输特性表达式,推导出在线圈偏移情况下最佳等效参数kr与n1的表达式,为WPT系统的补偿网络的优化设计提供理论依据。最终通过实物实验验证所提系统的恒压输出特性及其参数设计方法的正确性和有效性。

Compared with the multi-coil structure,the two-coil wireless power transfer(WPT)system shows shortcomings in transmission distance and transmission efficiency,but the transmission characteristics of the WPT system can be improved by increasing the order of the compensation network and the active control strategy.Different from the design of compensation network,the research of active control strategy has the problems of large system complexity and high control cost.Therefore,combined with the transformer T network model,this paper proposes a new method for compensating network parameters and transmission characteristics analysis of a two-coil WPT system with variable gain constant voltage characteristics,which lays a research foundation for multi-node WPT technology of sensor networks.Firstly,the equivalent model of transformer T-network is established,and the element parameter expression of S-S two-coil WPT system with constant voltage characteristic is given.Secondly,the new parameters-equivalent coupling coefficient kr and equivalent variable ratio n1 are defined,and a new method for determining the compensation network parameters of SP-S and SP-PS compensation structures with variable gain and constant voltage characteristics is proposed.Then,considering the direct influence of system parasitic resistance on transmission characteristics,the variation trend of voltage gain stability with equivalent parameters under coil offset and frequency oscillation is analyzed,and the optimal equivalent parameter expression under coil offset is derived.Finally,the experimental prototypes of two-coil WPT system with S-S,SP-S and SP-PS compensation structures are built to verify the correctness and effectiveness of the variable gain constant voltage output characteristics and analysis conclusions of the proposed system.Through theoretical analysis and experimental verification,the following conclusions can be drawn:(1)The proposed new design method of two-coil WPT system’s compensation network makes the output voltage gain of WPT system meet the target variable ratio,simplifies the parameter design method,increases the degree of freedom of system design,and makes the parameter selection more flexible.(2)The two-coil WPT system under coil offset will increase first and then decrease with the increase of equivalent variable ratio n1,and will also show the same trend with the increase of equivalent coupling coefficient kr.(3)Considering the direct influence of the parasitic resistance of the system on the transmission characteristics,the optimal equivalent parameter expression of WPT system with or without parallel resonant element CL under coil offset is obtained.(4)The transmission efficiency of the steady-state WPT system increases first and then decreases with the increase of 21n,the two-coil WPT system with CL increases first and then decreases with the increase of the equivalent coupling coefficient kr,and the WPT system without CL increases first and then decreases with the increase of 2rk.